EXTERNAL OHABAOTBBS AND HABITS 71
Their movements in the trees are very graceful, and Martin has given the following account of the activities of a slender Gibbon, living in the Zoological Gardens of London, in 1840 : " It is almost impossible to convey in words an idea of the quickness and graceful address of her movements: they may indeed be termed aerial, as she seems merely to touch in her progress the branches among which she exhibits her evolutions. In these feats her hands and arms are the sole organs of locomotion; her body hanging as if suspended by a rope, sustained by one hand (the right, for example), she launches herself, by an energetic movement, to a distant branch, which she catches with her left hand; but her hold is less than momentary: the impulse for the next launch is acquired : the branch then aimed at is attained by the right hand again, and quitted instantaneously and so on, in alternate succession. In this manner spaces of twelve and eighteen feet are cleared, with the greatest ease, and uninterruptedly, for hours together, without the slightest appearance of fatigue being manifested; and it is evident that, if more space could be allowed, distances very greatly exceeding eighteen feet would be as easily cleared; so that DuvaunceFs assertion that he has seen these animals launch themselves from one branch to another, forty feet asunder, startling as it is, may well be credited.
" Sometimes, on seizing a branch in her progress, she will throw herself, by the power of one arm only, completely round it, making a revolution with such rapidity as to almost deceive the eye, and continue her progress
with undiminished velocity. It is singular to observe how suddenly this Gibbon can stop, when the impetus